Stress-detecting element, sensor module, and electronic apparatus

ABSTRACT

A stress-detecting element includes a support body, a support film, a first piezoelectric element, first and second elastic parts. The support body has an opening part with first and second rectilinear sections extending parallel to each other. The support film blocks off the opening part. The first piezoelectric element straddles the first rectilinear section from an interior area to an exterior area of the opening part as seen in plan view. The first elastic part straddles the first rectilinear section from the interior area to the exterior area of the opening part. The second elastic part straddles the second rectilinear section from the interior area to the exterior area of the opening part. The first and second elastic parts respectively have first and second elastic end sections disposed in the interior area of the opening part and spaced apart from each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2011-121987 filed on May 31, 2011. The entire disclosure of JapanesePatent Application No. 2011-121987 is hereby incorporated herein byreference.

BACKGROUND

1. Technical Field

The present invention relates to a stress-detecting element fordetecting a shearing force that acts in a shearing direction andpressing force that acts in a direction orthogonal to the shearingforce, a sensor module provided with the stress-detecting element, andan electronic apparatus provided with the sensor module.

2. Related Art

in the past there has been known a gripping device that uses a robot armto grip and lift an object for which the weight and coefficient offriction are not known. In such a gripping device, it is necessary todetect a force (pressing force) that acts in a direction orthogonal tothe gripping surface and a force (shearing force) that acts in a planardirection of the gripping surface, in order to avoid damage to theobject and to avoid losing grip and dropping the object. There are knownsensors for detecting such forces (e.g., see Japanese Laid-Open PatentApplication Publication No. 2006-208248).

A tactile sensor described in the above mentioned publication has astructural assembly which includes a cantilever structure that extendsfrom an edge part of an opening provided in a sensor substrate. Thestructural assembly is composed of a planar sensing part, and a hingepart for coupling the sensing part and the sensor substrate together. Anelectroconductive magnetic film is formed on the sensing part of thestructural assembly, a piezoresistance film is formed on the hinge part,and the electroconductive magnetic film and the piezoresistance film aremade conductive. In this configuration, an electrode is disposed on thehinge part and the hinge part is bent by pressure, whereby electriccurrent generated by the piezoresistance of the hinge part flows from anelectrode. The tactile sensor has a plurality of structural assembliessuch as that described above formed on the sensor substrate, a portionof these structural assemblies being held erect in relation to thesensor substrate, and the other portion being held parallel to thesensor substrate. An elastic body is disposed on the sensor substrate,and the erect structural assemblies are embedded in the elastic body.

SUMMARY

In a tactile sensor such as that described in the above mentionedpublication, there are problems in that the configuration has acomplicated spatial structure in which the structural assembly of thecantilever structure stands erect, there are complicated manufacturingsteps for applying a magnetic field to bend or otherwise manipulate thestructural assembly of the cantilever structure during the manufacturethereof, and productivity is poor.

In response thereto, it is possible to consider a stress-detectingelement in which a membrane is disposed on the substrate having anopening part so as to block the opening part, arrange the piezoelectricelements along the interior and exterior of the membrane, and to coverthe upper part with an elastic film. Such a stress-detecting element canbe readily manufactured and made smaller because the film member forforming a membrane, the piezoelectric elements, and the elastic film arelayered and formed over the substrate in which the opening part isformed.

However, in such a stress-detecting element, there is a drawback in thatthe signal value outputted from the piezoelectric elements is reducedand detection precision is liable to be reduced when the bendingdistance of the membrane is short in the case that the elastic film isadded.

In view of the drawbacks such as those described above, an objective ofthe present invention is to provide a stress-detecting element, a sensormodule, and an electronic apparatus that have good productivity and highstress detection precision.

A stress-detecting element according to one aspect of the presentinvention includes a support body, a support film, a first piezoelectricelement, a first elastic part and a second elastic part. The supportbody has an opening part with a first rectilinear section and a secondrectilinear section extending parallel to each other. The support filmis disposed over the support body and blocks off the opening part. Thefirst piezoelectric element is disposed over the support film along thefirst rectilinear section of the opening part of the support body so asto straddle the first rectilinear section from an interior area of theopening part to an exterior area of the opening part as seen in planview along a film thickness direction of the support film. The firstpiezoelectric element is configured and arranged to output an electricsignal upon deformation. The first elastic part is disposed over thesupport film along the first rectilinear section of the opening part ofthe support body so as to straddle the first rectilinear section fromthe interior area of the opening part to the exterior area of theopening part as seen in plan view. The first elastic part has a firstelastic end section disposed in the interior area of the opening part asseen in plan view. The second elastic part is disposed over the supportfilm along the second rectilinear section of the opening part of thesupport body so as to straddle the second rectilinear section from theinterior area of the opening part to the exterior area of the openingpart as seen in plan view. The second elastic part has a second elasticend section disposed in the interior area of the opening part as seen inplan view. The second elastic end section is spaced apart from the firstelastic end section.

As used herein, the phrase “the first rectilinear section and the secondrectilinear section extending parallel to each other” in the presentaspect allows for slight error tolerance, and includes, in addition tothe configuration in which the first rectilinear section and the secondrectilinear section are perfectly parallel, configurations in which,e.g., the first rectilinear section and the second rectilinear sectionare slightly inclined yet generally parallel to each other.

In the present aspect, the stress-detecting element has the support filmformed in a state that blocks off the opening part and the support filmis disposed over the support body in which the opening part having thefirst rectilinear section and the second rectilinear section isdisposed. The first piezoelectric element disposed over the support filmso as to straddle the first rectilinear section from the inside to theoutside of the opening part. Also, the first elastic part that straddlesthe first rectilinear section and the second elastic part that straddlesthe second rectilinear section are disposed over the support body.Herein, as described above, the support film in the area within theopening part is referred to as a membrane.

In such a stress-detecting element, when a shearing force is applied tothe first elastic part and to the second elastic part, the first elasticpart and the second elastic part flexibly deform along the direction inwhich shearing force has been applied (detected direction of shearingforce), and strain is generated in the membrane. In the present aspect,the shearing force can be measured by using the first piezoelectricelement to detect the amount of bending of such a membrane.

In this case, the membrane is preferably bent (deformed) in the form ofa sinusoid in order to improve detection precision. For example, in thecase that a shearing force acts in the direction from the firstrectilinear section to toward the second rectilinear section, the firstrectilinear section side of the membrane deforms so as to enter into theopening part side, and the second rectilinear section side of themembrane deforms so as to lift away in the direction away from theopening part. On the other hand, in the case that a shearing force actsin the direction from the second rectilinear section toward the firstrectilinear section, the first rectilinear section of the membranedeforms so as to lift away and the second rectilinear section of themembrane deforms so as to enter into the opening part. Such membranedeformation is detected to make it possible to detect the direction inwhich the shearing force operates in addition to the magnitude of theshearing force.

In the case of a configuration in which the elastic body is disposed soas to cover the entire membrane, when the first rectilinear section sideof the membrane bends, the vicinity where the inflection point with thebending of the second rectilinear section is formed is obstructed fromdeforming by the rigidity of the elastic part, and the amount of bendingis reduced. In this case, the signal value outputted from the firstpiezoelectric element is also reduced and the precision of detecting theshearing force is reduced.

In response to the above, according to the present aspect, a gap isformed between the first elastic part and the second elastic part sincethe first elastic end section of the first elastic part and the secondelastic section of the second elastic part are spaced apart from eachother. In other words, there is a location in which the first elasticpart and the second elastic part do not exist in the center part of themembrane. In such a configuration, since the elastic part does not existover the support film between the first elastic part and the secondelastic part, displacement of the membrane is not obstructed. Therefore,an inflection point can be advantageously formed between the bending ofthe membrane formed by the first elastic part and the bending of themembrane formed by the second elastic part. In the case that, e.g.,shearing force is applied to the first elastic part and the secondelastic part from the first rectilinear section toward the secondrectilinear section, the position in which the first elastic part of themembrane is disposed thereby displaces considerably to the opening partside, and the position in which the second elastic part is disposeddisplaces considerably in the direction away from the opening part. As aresult, sinusoidal bending with considerable amplitude can be formed.Accordingly, the signal value outputted from the first piezoelectricelement is also increased, and detection precision can be improved.

The stress-detecting element of the present aspect has a simpleconfiguration in which the support film, the first piezoelectricelement, the first elastic part, and the second elastic part are merelydisposed over the support body. Therefore, manufacturing is simple andmanufacturing costs can also be reduced.

In the stress-detecting element of the present aspect, the first elasticend section of the first elastic part and the second elastic end sectionof the second elastic part are preferably parallel to the firstrectilinear section and the second rectilinear section as seen in planview.

In the same manner as the aspect described above, the phrase “the firstelastic end section and the second elastic end section are parallel tothe first rectilinear section and the second rectilinear section” in thepresent aspect includes, in addition to the configuration of a perfectlyparallel state, configurations in which at least one of the firstelastic end section and the second elastic end section is in a generallyparallel state so as to be slightly inclined in relation to the firstrectilinear section and the second rectilinear section.

Here, in the case that the first elastic end section and the secondelastic end section are not parallel, the bending of the membrane isliable to have different shapes depending on the location. For example,when a shearing force is applied along the +X direction from the firstrectilinear section toward the second rectilinear section and thebending state of the membrane is viewed along the Y direction, which isorthogonal to the X direction, there are cases in which the bendingstate in the position Y=a on the membrane and the bending shape in theposition Y=b (b≠a) are different shapes in the case that the firstelastic end section and the second elastic end section are not parallel.In such a case, the shearing force cannot accurately be detected. Evenwhen the first elastic end section and the second elastic end sectionare parallel, there may be cases in which the bending shape is differentdepending on the position on the membrane in the same manner as when theelastic end sections are not parallel to the first rectilinear section(second rectilinear section).

In response to the above, in the present aspect, the first elastic endsection, the second elastic end section, the first rectilinear section,and the second rectilinear section are parallel, as described above, andregardless of the Y coordinate, the bending shape of the membrane in theX direction is the same, and the shearing force can be accuratelydetected.

In the stress-detecting element of the present aspect, a distance fromthe first rectilinear section of the opening part to the first elasticend section is preferably equal to a distance from the secondrectilinear section to the second elastic end section as seen in planview.

With this arrangement, the stress that the first elastic part imparts tothe membrane, and the stress that the second elastic part imparts to themembrane are in different directions, and the magnitude of the stress issubstantially the same. Therefore, the amount of bending of the firstrectilinear section side of the membrane and the amount of bending ofthe second rectilinear section side are substantially the same amount ofbending, and the bending directions are opposite. Accordingly, themembrane can be made to bend in the shape of a sinusoid in which thecenter point of the membrane is the inflection point.

In the stress-detecting element of the present aspect, each of thedistance from the first rectilinear section of the opening part to thefirst elastic end section and the distance from the second rectilinearsection to the second elastic end section is preferably 10% to 30% of adistance from the first rectilinear section to the second rectilinearsection.

The membrane is preferably bent into a sinusoidal shape in order toincrease the amount of bending of the membrane. In other words, it ispreferred that the amplitude of the membrane be maximum at positionscorresponding to X=T/4 and X=3T/4, with a position corresponding toX=T/2 being the inflection point, where the +X direction is thedirection from the first rectilinear section to the second rectilinearsection on the membrane, the X coordinate of the first rectilinearsection is 0, and the X coordinate of the second rectilinear section isT.

In the case that the distance from the first rectilinear section to thefirst elastic end section, and the distance from the second rectilinearsection to the second elastic end section are less than 10% of thedistance from the first rectilinear section to the second rectilinearsection, stress from the first elastic part and the second elastic partis not suitably transmitted to the membrane, and the amount of bendingof the membrane is reduced. On the other hand, in the case that thedistance from the first rectilinear section to the first elastic endsection, and the distance from the second rectilinear section to thesecond elastic end section are greater than 30% of the distance from thefirst rectilinear section to the second rectilinear section, thepositions corresponding to X=T/4 and X=3T/4 in which the amplitude ofthe membrane is maximum cannot achieve sufficient amplitude because thefirst elastic part and the second elastic part covering the membrane isrelatively large, and the amount of bending of the membrane is reduced.In response to the above, in the case that the distance from the firstrectilinear section to the first elastic end section and the distancefrom the second rectilinear section to the second elastic end sectionare within a range of 10% to 30% of the distance from the firstrectilinear section to the second rectilinear section as in the presentaspect, the bending of the membrane is not obstructed, and sufficientstress is transmitted from the first elastic part and the second elasticpart. A configuration is further preferably used in which the firstelastic end section and the second elastic end section are disposed suchthat the distance from the first rectilinear section to the firstelastic end section and the distance from the second rectilinear sectionto the second elastic end section are about 20% to 25% of the distancefrom the first rectilinear section to the second rectilinear section,i.e., in the vicinity of the positions corresponding to X=T/4 and X=3T/4in which the amplitude of the membrane is maximum, whereby the amount ofbending of the membrane can be maximized. In this case, a strongersignal can be outputted from the first piezoelectric element, anddetection precision can be further improved.

In the stress-detecting element of the present aspect, the first elasticpart preferably covers the first piezoelectric element.

In a configuration in which the first elastic part covers only on aportion of the first piezoelectric element, the amount of bending in theportion of the first piezoelectric element on which the first elasticpart does not exist is decreased. In this case, the bending of the firstpiezoelectric element is reduced and the outputted signal is weakened.In response to this situation, the present aspect has a configuration inwhich the first elastic part preferably covers the entire firstpiezoelectric element. Therefore, the bending of the first piezoelectricelement is increased, signal strength can be increased, and thedetection precision can be further improved.

The stress-detecting element of the present aspect preferably furtherincludes a second piezoelectric element disposed over the support filmalong the second rectilinear section of the opening part of the supportbody so as to straddle the second rectilinear section from the interiorarea of the opening part to the exterior area of the opening part asseen in plan view. The second piezoelectric element is preferablyconfigured and arranged to output an electric signal upon deformation.

In the present aspect, the second piezoelectric element is disposedalong the second rectilinear section. Therefore, a shearing force can bedetected by sum of the signal values of both the first piezoelectricelement and the second piezoelectric element, and the detectionprecision can be further improved.

In the stress-detecting element of the present aspect, the opening partpreferably further includes a third rectilinear section and a fourthrectilinear section extending orthogonal to the first rectilinearsection and the second rectilinear section. The stress-detecting elementpreferably further includes a third piezoelectric element, a thirdelastic part and a fourth elastic part. The third piezoelectric elementis preferably disposed over the support film along the third rectilinearsection of the opening part of the support body so as to straddle thethird rectilinear section from the interior area of the opening part tothe exterior area of the opening part as seen in plan view. The thirdpiezoelectric element is preferably configured and arranged to output anelectric signal upon deformation. The third elastic part is preferablydisposed over the support film along the third rectilinear section ofthe opening part of the support body so as to straddle the thirdrectilinear section from the interior area of the opening part to theexterior area of the opening part when viewed in the plan view. Thethird elastic part preferably has a third elastic end section disposedin the interior area of the opening part as seen in plan view. Thefourth elastic part is preferably disposed over the support film alongthe fourth rectilinear section of the opening part of the support bodyso as to straddle the fourth rectilinear section from the interior areaof the opening part to the exterior area of the opening part as seen inplan view. The fourth elastic part preferably has a fourth elastic endsection disposed in the interior area of the opening part as seen inplan view, the fourth elastic end section being spaced apart from thethird elastic end section.

With this arrangement, in addition to detection of shearing force in theX direction from the first rectilinear section toward the secondrectilinear section, shearing force in the Y direction from the thirdrectilinear section toward the fourth rectilinear section can bedetected by the third piezoelectric element. The direction and magnitudeof the shearing force along the X direction and the direction andmagnitude of the shearing force along the Y direction are calculatedbased on signals from the first piezoelectric element and the thirdpiezoelectric element, and these data are subjected to a vectorcalculation, whereby the direction and magnitude of the shearing forcethat acts in a two-dimensional plane can be calculated.

The stress-detecting element of the present aspect preferably furtherincludes a fourth piezoelectric element disposed over the support filmalong the fourth rectilinear section of the opening part of the supportbody so as to straddle the fourth rectilinear section from the interiorarea of the opening part to the exterior area of the opening part asseen in plan view. The fourth piezoelectric element is preferablyconfigured and arranged to output an electrical signal upon deformation.

In the present aspect, a shearing force in the Y direction from thethird rectilinear section toward the fourth rectilinear section can beaccurately detected based on signal values outputted from both the thirdpiezoelectric element and the fourth piezoelectric element in the samemanner as described above.

In the stress-detecting element of the present aspect, the first elasticpart, the second elastic part, the third elastic part, and the fourthelastic part are preferably integrally formed as one-piece, unitarymember.

According to the present aspect, the first elastic part, the secondelastic part, the third elastic part, and the fourth elastic part areintegrally formed as one-piece, unitary member. In such a configuration,a slit-shaped gap is disposed in these integrally formed elastic partsin order to form a gap between the elastic parts, whereby thestress-detecting element having the configuration described above can bereadily formed, manufacturing efficiency can be improved, and theconfiguration can be simplified.

A sensor module according to another aspect of the present inventionincludes a sensor array having a plurality of the stress-detectingelements described above that are arranged in a form of an array.

In the present aspect, the sensor module is provided with the sensorarray in which stress-detecting elements are arranged in the form of anarray. Here, the stress-detecting elements are readily manufactured andhave high shearing-force precision, as described above. Therefore, thesensor module is readily manufactured and shearing force can be detectedwith high precision using a plurality of stress-detecting elements.

An electronic apparatus according to another aspect of the presentinvention includes the sensor module described above, and a signalprocessing part configured and arranged to process electrical signalsoutputted from the sensor module.

The electronic apparatus of the present aspect includes the sensormodule described above. Therefore, various processing can be carried outbased on a high-precision shearing force detection signal outputted fromthe sensor module.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a plan view showing the schematic configuration of thestress-detecting element of a first embodiment of the present invention;

FIG. 2 is a cross-sectional view showing the schematic configuration ofthe stress-detecting element of the first embodiment;

FIG. 3 is a view showing the state in which the object has made contactwith the stress-detecting element, wherein FIG. 3A is a view showing thestate prior to deformation of the membrane, and FIG. 3B is a viewshowing the state in which the membrane has been deformed by shearingforce;

FIG. 4 is a view showing the state in which the object has made contactwith the stress-detecting element, wherein FIG. 4A is a view showing thestate in which the membrane has been deformed by positive pressure, andFIG. 4B is a view showing the state in which the membrane has beendeformed by both shearing force and positive pressure;

FIG. 5 is a view schematically showing the electric potential generatedby the piezoelectric film, wherein FIG. 5A is a view showing the statein which the piezoelectric film has not deformed, FIG. 5B is a viewshowing the state in which the piezoelectric film has been elongated,and FIG. 5C is a view showing the state in which the piezoelectric filmhas been compressed;

FIG. 6 is a plan view in which a portion of a tactile sensor of a secondembodiment has been enlarged;

FIG. 7 is a cross-sectional view in which a portion of the tactilesensor of the second embodiment has been sectioned;

FIG. 8 is a device block view showing the schematic configuration of agripping device of a third embodiment;

FIG. 9 is a view showing the relationship between the pressing force andthe shearing force that act on a tactile sensor in the grippingoperation of the gripping device;

FIG. 10 is a block view showing the schematic configuration of an ironof a fourth embodiment;

FIG. 11 is a perspective view showing the schematic configuration of anotebook computer of a fifth embodiment; and

FIG. 12 is a plan view showing the stress-detecting element in anotherembodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

The stress-detecting element of a first embodiment of the presentinvention is described below with reference to the accompanyingdrawings.

1. Configuration of Stress-Detecting Element

FIG. 1 is a plan view showing the schematic configuration of thestress-detecting element 100 of the first embodiment; and FIG. 2 is across-sectional view of the stress-detecting element 100.

The stress-detecting element 100 is configured by layering a supportfilm 12, piezoelectric elements 13, and an elastic body 14 composed of afirst elastic part, a second elastic part, a third elastic part, and afourth elastic part of the present invention, on a sensor substrate 11,which is the support body of the present invention, as shown in FIG. 1.In FIG. 1, portions of the piezoelectric elements 13 are shown in solidlines to better understand the structures thereof although thepiezoelectric elements 13 are disposed below the elastic body 14 asshown in FIG. 2. The stress-detecting element 100 is an element fordetecting shearing force and positive pressure applied when an objectmakes contact with the elastic body 14.

Configuration of Sensor Substrate

The sensor substrate 11 is composed of, e.g., Si, and is formed to athickness dimension of, e.g., 200 μm. An opening part 111 is formed inthe sensor substrate 11, as shown in FIGS. 1 and 2. The opening part 111is formed in a square shape when the sensor substrate 11 is viewed fromabove (sensor plan view) from the thickness direction of the sensorsubstrate 11, and the sides of the square shape are composed of a firstrectilinear section 111A, a second rectilinear section 111B, a thirdrectilinear section 111C, and a fourth rectilinear section 111D. In thepresent embodiment, the opening part 111 is formed such that the lengthof one side is, e.g., 500 μm.

Configuration of Support Film

The support film 12 is formed from a bilayer structure (not shown)composed of an SiO₂ layer formed to a thickness dimension of, e.g., 3 μmthe sensor substrate 11, and a ZrO₂ layer having a thickness dimensionof, e.g., 400 nm layered on the SiO₂ layer. In this case, the ZrO₂ layeris a layer formed for preventing the piezoelectric film 132 from peelingaway when the later-described piezoelectric element 13 is baked andformed. In other words, in the case that the piezoelectric film 132 isformed from, e.g., PZT, the Pb contained in the piezoelectric film 132diffuses into the SiO₂ layer during baking when a ZrO₂ layer has notbeen formed, the melting point of the SiO₂ layer is reduced, air bubblesform in the surface of the SiO₂ layer, and the PZT peels away due to theair bubbles. Another problem in the case that a ZrO₂ layer is notpresent is that the bending efficiency is reduced or otherwise degradedin relation to strain on the piezoelectric film 132. It is possible toavoid peeling of the piezoelectric film 132, reduction in the bendingefficiency, and other drawbacks in the case that a ZrO₂ layer is formedon the SiO₂ layer in response to this situation.

Also, when the sensor is viewed from above as shown in FIG. 1, the areaof the support film 12 that is blocked off by the opening part 111 shallbe referred to as a membrane 121 in the following description.

Configuration of Piezoelectric Element

The piezoelectric elements (first piezoelectric element 13A to fourthpiezoelectric element 13D) 13 are formed on the membrane 121 along therectilinear sections 111A to 111D of the opening part 111 and in theshape of a rectangle in which the long sides of the elements are in thesame direction as the rectilinear direction of the rectilinear sections111A to 111D. The piezoelectric elements 13 are arranged so as tostraddle from the interior area of the opening part 111 to the exteriorarea of the opening part 111 with the rectilinear sections 111A to 111Dof the opening part 111 disposed therebetween, respectively. In thepresent embodiment, the piezoelectric element 13 disposed along thefirst rectilinear section 111A is the first piezoelectric element 13A,the piezoelectric element 13 disposed along the second rectilinearsection 111B is the second piezoelectric element 13B, the piezoelectricelement 13 disposed along the third rectilinear section 111C is thethird piezoelectric element 13C, and the piezoelectric element 13disposed along the fourth rectilinear section 111D is the fourthpiezoelectric element 13D.

These piezoelectric elements 13 are configured by layering a lowerelectrode 131, a piezoelectric film 132, and an upper electrode 133.

The piezoelectric film 132 is formed by forming, e.g., lead zirconatetitanate (PZT) into the shape of a film having a thickness dimension of,e.g., 500 nm. In the present embodiment, PZT is used as thepiezoelectric film 132, but any material can be used provided that thematerial is capable of generating a charge when the film undergoes achange in stress, and examples of the material that may be used includelead titanate (PbTiO₃), lead zirconate (PbZrO₃), lead lanthanum titanate((Pb,La)TiO₃), aluminum nitride (AlN), zinc oxide (ZnO), andpolyvinylidene fluoride (PVDF). The piezoelectric film 132 generates adifference in electric potential between the lower electrode 131 and theupper electrode 133 in accordance with the amount of bending when thesupport film bends due to shearing force. An electric current from thepiezoelectric film 132 flows to the lower electrode 131 and the upperelectrode 133, and an electric signal is outputted.

The lower electrode 131 and the upper electrode 133 are electrodesformed so as to sandwich the piezoelectric film 132 in the thicknessdirection. The lower electrode 131 is formed on the surface facing themembrane 121 of the piezoelectric film 132, and the upper electrode 133is formed on the surface opposite of the surface on which the lowerelectrode 131 is formed.

The lower electrode 131 is a film-shaped electrodes formed to athickness dimension of, e.g., 200 nm, and is formed straddling theinside and outside of the membrane 121 along the direction orthogonal tothe respective rectilinear section 111A to 111D on which thepiezoelectric elements 13 are formed. The lower electrode 131 may be anyelectrode provided that the lower electrode is an electroconductive thinfilm having electroconductivity, but in the present embodiment, forexample, a structured film composed of Ti/Ir/Pt/Ti layers is used.

The upper electrode 133 is a film-shaped electrode formed to a thicknessdimension of, e.g., 50 nm. The upper electrode 133 covers the areabetween the end parts of the piezoelectric film 132 in the lengthwisedirection and is formed parallel to the rectilinear sections 111A to111D on which the piezoelectric elements 13 are formed. A draw-out part133A is formed on the end part of the upper electrode 133 in thelengthwise direction. The use of such an electrode pattern makes itpossible to readily draw out the electric signal outputted from thepiezoelectric elements 13 without covering the electrode with aninsulation film or the like and without a portion in which the lowerelectrode 131 and the upper electrode 133 make direct contact with eachother.

Any material may be used as the upper electrode 133 provided that thematerial is an electroconductive thin film, similarly with respect tothe lower electrode 131, and in the present embodiment, an Ir thin filmis used.

In such a piezoelectric element 13, the portion in which the lowerelectrode 131, the piezoelectric film 132, and the upper electrode 133are superimposed along the film direction is a piezoelectric layeringportion 134 for detecting the amount of bending of the support film.

Configuration of Elastic Body

The elastic body 14 is a film formed so as to cover the support film 12and the piezoelectric elements 13 as described above. In the presentembodiment, for example, polydimethylsiloxane (PDMS) is used as theelastic body 14, but no limitation is imposed thereby, and the elasticbody may also be formed from a synthetic resin or the like havingelasticity, and or another elastic material. The thickness dimension ofthe elastic body 14 is not particularly limited, and is, e.g., 300 μm.

The elastic body 14 has a square-shaped slit 141 formed in the centerarea of the opening part 111 when the sensor is viewed from above. Inother words, the elastic body 14 is provided with a first elastic part141A disposed straddling the inside and outside of the opening part 111along the first rectilinear section 111A, a second elastic part 141B ofthe second rectilinear section 111B that is disposed straddling theinside and outside of the opening part 111, a third elastic part 141C ofthe third rectilinear section 111C that is disposed straddling theinside and outside of the opening part 111, and a fourth elastic part141D of the fourth rectilinear section 111D that is disposed straddlingthe inside and outside of the opening part 111. The slit 141 is formedby the end part of the first elastic part 141A on the internalperipheral side of the opening part 111 (a first elastic end section143A), the end part of the first elastic part 141B on the internalperipheral side of the opening part 111 (a second elastic end section143B), the end part of the first elastic part 141C on the internalperipheral side of the opening part 111 (a third elastic end section143C), and the end part of the first elastic part 141D on the internalperipheral side of the opening part 111 (a fourth elastic end section143D).

In this case, the first elastic end section 143A and the second elasticend section 143B are parallel to the first rectilinear section 111A (thesecond rectilinear section 111B) and spaced apart from each other toface each other across an elastic-parts gap Gx. The third elastic endsection 143C and the fourth elastic end section 143D are parallel to thethird rectilinear section 111C (the fourth rectilinear section 111D) andspaced apart from each other to face each other across an elastic-partsgap Gy (second elastic-parts gap).

In the first elastic part 141A (second elastic part 141B), the distanceL from the first rectilinear section 111A (the second rectilinearsection 111B) to the first elastic end section 143A (the second elasticend section 143B) is preferably formed so as to be about 10% to 30%,more preferably 20% to 25%, of the opening dimension (the distance fromthe first rectilinear section 111A to the second rectilinear section111B) Lw of the opening part 111.

In the case that the distance L from the first rectilinear section 111A(111B) to the first elastic end section 143A (second elastic end section143B) is less than 10% of the opening dimension Lw, when the shearingforce and stress acts on the elastic body 14 and causes elasticdeformation, stress that is commensurate to the elastic deformation isnot sufficiently transmitted from the first elastic part 141A (secondelastic part 141B) to the membrane 121, and the amount of bending of themembrane 121 is reduced. On the other hand, in the case that thedistance L from the first rectilinear section 111A (second rectilinearsection 111B) to the first elastic end section 143A (second elastic endsection 143B) is greater than 30% of the opening dimension Lw, the sizeof a hollow part 144 is reduced. In this case, the bending of themembrane 121 that corresponds to the portion in which the hollow part144 is disposed is obstructed by the first elastic part 141A and thesecond elastic part 141B, and the amount of bending of the membrane 121is reduced. As described above, when the bending of the membrane 121 isreduced, the signal value outputted from the first piezoelectric element13A and/or the second piezoelectric element 13B is reduced, anddetection precision is degraded.

In contrast, in the case that the distance L from the first rectilinearsection 111A (second rectilinear section 111B) to the first elastic endsection 143A (second elastic end section 143B) is in a range of 10% to30%, preferably 20% to 25%, of the opening dimension Lw, the firstelastic end section 143A and the second elastic end section 143B arepositioned in the vicinity of the location in which the bending of themembrane 121 is maximum, and the amount of bending of the membrane 121is increased. Accordingly, the signal outputted from the firstpiezoelectric element 13A and/or the second piezoelectric element 13B isincreased and the detection precision can be improved.

For the same reason, in relation to the third elastic part 141C and thefourth elastic part 141D, the distance L from the third rectilinearsection 111C (fourth rectilinear section 111D) to the third elastic endsection 143C (fourth elastic end section 143D) is preferably in a rangeof 10% to 30%, more preferably 20% to 25%, of the opening dimension (thedistance from the third rectilinear section 111C to the fourthrectilinear section 111D) Lw.

In the present embodiment, the length dimension Lw of one side of theopening part 111 (the distance from the first rectilinear section 111Ato the second rectilinear section 111B, and the distance from the thirdrectilinear section to the fourth rectilinear section) is 500 μm, andthe distance L from the rectilinear sections 111A to 111D of the openingpart to the slit 141 is 100 μm.

2. Operation of Stress-Detecting Element

The operation of the stress-detecting element 100 described above willnext be described with reference to the accompanying drawings.

With the stress-detecting element 100, when a shearing force is appliedalong the X direction, the shearing force is detected by the firstpiezoelectric element 13A and the second piezoelectric element 13B; andwhen a shearing force is applied along the Y direction, the shearingforce is detected by the third piezoelectric element 13C and the fourthpiezoelectric element 13D. When a pressing force is applied orthogonalto the sensor substrate 11, the pressing force is detected by the firstpiezoelectric element 13A, the second piezoelectric element 13B, thethird piezoelectric element 13C, and the fourth piezoelectric element13D.

Here, as examples, the direction of detection of the shearing force willbe described for the case in which a shearing force is applied in the Xdirection of the membrane 121, and for the case in which when positivepressure is applied in addition to the shearing force. In the case inwhich the shearing force is applied in the Y direction, the shearingforce is detected by the same operation, and a description thereof isomitted.

FIG. 3 is a view showing the state in which an object Z has made contactwith the stress-detecting element 100, wherein FIG. 3A is a view showingthe state prior to deformation of the membrane 121, and FIG. 3B is aview showing the state in which the membrane has been deformed byshearing force. FIG. 4A is a view showing the state of deformation ofthe membrane 121 when a positive pressure has been applied from thestate of FIG. 3A, and FIG. 4B is a view showing the state in which themembrane 121 has been deformed when both shearing force and positivepressure have been applied in the +X direction from the state of FIG.3A.

The stress-detecting element 100 is configured such that when the objectZ makes contact with the elastic body 14, as shown in FIG. 3A, andshearing force is applied in the direction of the arrow P1, as shown inFIG. 3B.

In other words, when a shearing force is generated in the elastic body14, the surface on the −X side of the membrane 121 is pressed to theopening part 111 side by the first elastic part 141A. Therefore, amoment force into the opening part 111 is generated as indicated by thearrow M1. In the case of the surface on the +X side, on the other hand,the surface on the +X side of the membrane 121 is pulled away by thesecond elastic part 141B in a direction away from the opening part 111,and a moment force that lifts away from the opening part 111 isgenerated as indicated by the arrow M2.

An inflection point appears at the center point of the position wherethe slit 141 is disposed, more specifically, the center point of themembrane 121, and the membrane 121 curves in the form of a sinusoid.

In the case that positive pressure is applied to the elastic body 14,the first elastic part 141A and the second elastic part 141B press themembrane 121 to the opening part side, as shown in FIG. 4A, and themembrane 121 therefore bends so as to sink into the opening part 111side.

In the case that both shearing force and positive pressure are appliedto the elastic body 14, a deformed state of the membrane 121 such asthat shown in FIG. 3B and a deformed state of the membrane 121 such asthat shown in FIG. 4A occur simultaneously, and as a result, the entiremembrane 121 sinks into the opening part 111, and bending is generatedin the form of a sinusoid, as shown in FIG. 4B.

When the membrane 121 bends in the manner described above, an electricsignal that corresponds to the bending direction and bending amount ofthe membrane 121 is outputted by the piezoelectric elements 13.

FIG. 5 is a view schematically showing the electric potential generatedby the piezoelectric film 132, wherein FIG. 5A is a view showing thestate in which the piezoelectric film 132 has not deformed, FIG. 5B is aview showing the state in which the piezoelectric film 132 has beenelongated, and FIG. 5C is a view showing the state in which thepiezoelectric film 132 has been compressed.

In order to detect the pressing force and shearing force using thestress-detecting element 100 as described above, voltage is appliedbetween the upper electrode 133 and the lower electrode 131 in advance,and the electrodes are polarized with the application of the voltage, asshown in FIG. 5A. In this state, a difference in electric potential isgenerated in the piezoelectric film 132 when bending is generated in themembrane 121.

In the case that the piezoelectric elements 13 bend to the opening part111 side, a pulling stress is generated in the piezoelectric film 132 inthe in-plane direction of the piezoelectric film 132, and the filmthickness is reduced, as shown in FIG. 5B. Thereby, in the piezoelectricfilm 132, the magnitude of polarization moment is reduced, a positivecharge sufficient to offset the difference between the initialpolarization value is generated in the contact surface with the upperelectrode 133, and a negative charge is generated in the contact surfacewith the lower electrode 131. Therefore, an electric current flows inthe direction from the lower electrode 131 to the upper electrode 133and is outputted as an electric signal.

On the other hand, in the case that the piezoelectric elements 13 bendin the direction away from the opening part 111, compression stress isgenerated in the piezoelectric film 132, and the thickness of thepiezoelectric film 132 increases, as shown in FIG. 5C. Thereby, in thepiezoelectric film 132, the magnitude of polarization moment isincreased, a negative charge is generated in the upper electrode 133,and a positive charge is generated in the lower electrode 131.Accordingly, an electric current flows in the direction from the upperelectrode 133 to the lower electrode 131, and is outputted as anelectric signal.

3. Method for Calculating Stress in Stress-Detecting Element

The method for calculating the positive pressure and the shearing forcewhen the stress-detecting element 100 has operated as described abovewill next be described.

In the stress-detecting element 100 of the present embodiment, inadvance, e.g., during manufacture of the stress-detecting element 100 a,a pressing force only is applied to the elastic body 14 with the appliedpressing force being varied, and the signal values (reference positivepressure signal value (V_(top))) outputted from the piezoelectricelements 13 in response to the pressing forces are measured. Herein, themembrane 121 is formed into a uniform film, the piezoelectric elements13 are disposed in positions equidistant from the center of the membrane121, and the piezoelectric elements 13 are each formed into the sameshape. Therefore, the reference positive pressure signal values(V_(top)) outputted from the piezoelectric elements 13 in the case thatonly positive pressure is applied are the same value.

Likewise, in advance, a shearing force only is applied to the elasticbody 14 in the X direction with the applied shearing force being varied,and the signal values (reference X shearing signal values (V_(A0),V_(B0))) outputted from the first piezoelectric element 13A and thesecond piezoelectric element 13B in response to the shearing forces aremeasured. Similarly, a shearing force only is applied to the elasticbody 14 in the Y direction, the applied shearing force is varied, andthe signal values (reference Y shearing signal values (V_(C0), V_(D0)))outputted from the third piezoelectric element 13C and the fourthpiezoelectric element 13D in response to the shearing forces aremeasured. Furthermore, calculated at this time are: a reference Xdifferential absolute value (|V_(A0)−V_(B0)|), which is the absolutevalue of the signal differential value in response to the shearing forcealong the X direction; and a reference Y differential absolute value(|V_(C0)−V_(D0)|), which is the signal differential value in response tothe shearing force along the Y direction.

The signal output values (V_(A), V_(B), V_(C) V_(D)) from thepiezoelectric elements 13 (13A, 13B, 13C, 13D) are measured for the casein which the object Z makes contact with the elastic body 14 and themembrane 121 deforms in the manner shown in FIGS. 4B and 5.

Here, the first piezoelectric element 13A and the second piezoelectricelement 13B output a signal value based on the total of the positivepressure and the shearing force in the X direction, and the thirdpiezoelectric element 13C and the fourth piezoelectric element 13Doutput a signal value based on the total of the positive pressure andthe shearing force in the Y direction. In other words, the signal outputvalues (V_(A), V_(B), V_(C), V_(D)) of the piezoelectric elements 13 areexpressed as the combination of the reference positive pressure signalvalue V_(top) and the reference X shearing signal values (V_(A0),V_(B0)), and a combination of the reference positive pressure signalvalue V_(top) and the reference Y shearing signal values (V_(C0),V_(D0)), as shown in the formulas (1) to (4) below.Formulas (1) to (4)V _(A) =V _(top) +V _(A0)  (1)V _(B) =V _(top) +V _(B0)  (2)V _(C) =V _(top) +V _(C0)  (3)V _(D) =V _(top) +V _(D0)  (4)

Therefore, eliminating V_(top) by the difference between the formula (1)and formula (2) enables the direction of the shearing force in the Xdirection to be determined, and the magnitude of the shearing force inthe X direction to be determined from the absolute value of thedifferential value. V_(A0) and V_(B0) have opposite signs and theabsolute values are substantially the same. Therefore, the V_(top) canbe calculated from the formula (1) or the formula (2), and the magnitudeof the positive pressure can be obtained.

In the same manner, the direction and magnitude of the shearing force inthe Y direction can be obtained from the difference between formulas (3)and (4), and V_(C0) and V_(D0) thus obtained are substituted intoformula (3) or formula (4), whereby V_(top) that corresponds to themagnitude of the positive pressure can be obtained.

4. Effect of First Embodiment

As described above, the stress-detecting element 100 of the firstembodiment comprises: the sensor substrate 11 in which the opening part111 having the first rectilinear section 111A and the second rectilinearsection 111B is disposed; the support film 12 provided with the membrane121 that blocks off the opening part 111; the piezoelectric elements 13disposed along first rectilinear section 111A and so as to straddle thefirst rectilinear section 111A across the inside and outside of themembrane 121; the first elastic part 141A disposed across the inside andoutside of the membrane 121 so as to straddle the first rectilinearsection 111A; and the second elastic part 141B disposed across theinside and outside of the membrane 121 so as to straddle the secondrectilinear section 111B. In such a configuration, the first elasticpart 141A presses the membrane 121 of the opening part 111 side, and thesecond elastic part 141B pulls the membrane 121 in the direction awayfrom the opening part 111 in the case that the shearing force is appliedtoward, e.g., the +X direction when the object Z makes contact with andshearing force is applied to the first elastic part 141A and the secondelastic part 141B along the X direction. In the case that shearing forceis applied in the −X direction, the first elastic part 141A pulls themembrane 121 away from the opening part 111 and the second elastic part141B presses the membrane 121 into the opening part 111. As describedabove, the first elastic part 141A and the second elastic part 141Bimpart a force to the membrane 121 in opposite directions, the centerposition of the membrane 121 (the position corresponding to theelastic-parts gap Gx) forms an inflection point, and the entire membrane121 bends in a sinusoidal shape.

The elastic-parts gap Gx is disposed between the first elastic endsection 143A of the first elastic part 141A and the second elastic endsection 143B of the second elastic part 141B, and the elastic body 14 isnot disposed on the membrane 121 in the elastic-parts gap Gx. Therefore,the membrane 121 can readily deform without being obstructed by theelastic body 14, and the amount of bending of the membrane 121 isincreased. Accordingly, the bending of the first piezoelectric element13A is also increased, the signal value outputted from the firstpiezoelectric element 13A is increased, and detection precision can befurther improved.

The stress-detecting element 100 can be readily formed by layering thesupport film 12, the piezoelectric elements 13, and the elastic body 14on the sensor substrate 11, as described above. Therefore, manufacturingefficiency is favorable, and manufacturing costs can also be reduced.

With the stress-detecting element 100 of the present embodiment, thefirst elastic end section 143A of the first elastic part 141A, thesecond elastic end section 143B of the second elastic part 141B, thefirst rectilinear section 111A, and the second rectilinear section 111Bare parallel to each other. The distance L from the first rectilinearsection 111A to the first elastic end section 143A is the same as thedistance L from the second rectilinear section 111B to the secondelastic end section 143B.

Therefore, the bending shape of the membrane 121 can be made uniform,and detection of the shearing force and the positive pressure can becarried out with high precision regardless of the Y coordinate when theshearing force acts on the elastic body 14 in the X direction.

The distance L described above is furthermore formed to be 20% of thelength dimension of one side of the opening part 111 (the dimension Lwfrom the first rectilinear section 111A to the second rectilinearsection 111B). Specifically, the distance L is formed within a range of10% to 30% of the distance Lw.

Accordingly, sufficient stress required for bending the membrane 121 canbe transmitted from the first elastic part 141A and the second elasticpart 141B to the membrane 121, and bending of the membrane 121 is notobstructed because the elastic body 14 is not formed in the center areaof the membrane 121, which is in the vicinity of the inflection point.Therefore, the membrane 121 can be advantageously bent by the firstelastic part 141A and the second elastic part 141B, and detectionprecision can be further improved.

The first elastic part 141A, the second elastic part 141B, the thirdelastic part 141C, and the fourth elastic part 141D are formed so as tocover the first piezoelectric element 13A, the second piezoelectricelement 13B, the third piezoelectric element 13C, and the fourthpiezoelectric element 13D, respectively.

In such a configuration, the piezoelectric elements 13 are protected bythe first elastic part 141A, the second elastic part 141B, the thirdelastic part 141C, and the fourth elastic part 141D, and thepiezoelectric elements 13 can be made to bend in a stable manner.

In the present embodiment, the first piezoelectric element 13A, thesecond piezoelectric element 13B, the third piezoelectric element 13C,and the fourth piezoelectric element 13D are disposed so as tocorrespond to the rectilinear sections 111A to 111D, respectively, ofthe opening part 111.

Accordingly, shearing force in the X direction can be detected withbetter precision using the signals outputted from both the firstpiezoelectric element 13A and the second piezoelectric element 13B, andshearing force in the Y direction can be detected with better precisionusing the signals outputted from both the third piezoelectric element13C and the fourth piezoelectric element 13D.

Furthermore, the use of the stress-detecting element 100 makes itpossible to calculate the differential value between V_(A0) and V_(B0)and the differential value between V_(C0) and V_(D0) from the signalvalues (V_(A), V_(B), V_(C), V_(D)) outputted from the piezoelectricelements 13, whereby the direction and magnitude of shearing force canbe readily calculated, and positive pressure can also be readilycalculated.

The first elastic part 141A, the second elastic part 141B, the thirdelastic part 141C, and the fourth elastic part 141D are formed inpositions of the elastic body 14 that overlap the center area of themembrane 121 as seen in plan view of the sensor, and are furthermoreintegrally formed in the shape of a square slit 141. The formation ofthe piezoelectric elements 14 can be facilitated by the use of such aconfiguration, the efficiency of manufacturing the stress-detectingelement 100 can be improved, and manufacturing costs can be reduced.

Second Embodiment

Next, a tactile sensor, which is a sensor module provided with thestress-detecting element 100, will be described with reference to theaccompanying drawings, using a stress-detecting element 100 such as thatdescribed above as an application example.

FIG. 6 is a plan view in which a portion of the tactile sensor of thesecond embodiment has been enlarged. FIG. 7 is a cross-sectional view inwhich a portion of the tactile sensor has been sectioned.

The tactile sensor 200 is provided with a plurality of thestress-detecting elements 100 of the first embodiment, as shown in FIG.6. These stress-detecting elements 100 are provided in a sensor array210 arranged in the form of an array, e.g., a matrix, on sensorsubstrate 11, which constitutes the support body of the presentinvention. Here, in these stress-detecting elements 100, the sensorsubstrate 11, the support film 12, and the elastic body 14 are composedof shared members. Specifically, a plurality of opening parts 111arranged in the form of a matrix is formed on a single sensor substrate11, and a contiguous support film 12 is formed on the entire surface ofone side of the sensor substrate 11. The membrane 121 covering each ofthe opening parts 111 is formed thereby. The elastic body 14 disposed onthe support film 12 is also shared in the stress-detecting elements 100,the elastic body 14 is formed so as to cover the entire surface of thesupport film 12, and a slit 141 is formed in the center area of theopening parts 111 of the stress-detecting elements 100.

A restriction groove 142 is formed in the elastic body 14, as shown inFIG. 7, between the stress-detecting elements 100. The restrictiongroove 142 is formed to a predetermined depth dimension from the surfaceof the elastic body 14 in contact with an object toward the support film12. With such a tactile sensor 200, the elastic body 14 of thestress-detecting elements 100 is separated by the restriction groove142, and the bending of the elastic body 14 of a stress-detectingelement 100 is not transmitted to the elastic body 14 of adjacentstress-detecting elements 100.

In FIG. 7, the restriction groove 142 of the elastic body 14 may beformed to a depth dimension of, e.g., about ¾ the film thickness of theelastic body 14 from the contact surface that can make contact with anobject, but no limitation is imposed thereby, and it is also possible touse a configuration in which the restriction groove 142 is formed to thesurface of the support film 12.

Furthermore, an example is shown in which the restriction groove 142 isformed in a rectangular ring that surrounds the stress-detectingelements 100 in a plan view of the sensor as shown in FIG. 6, but nolimitation is imposed thereby, and it is also possible to use aconfiguration in which, e.g., the restriction groove is formed so as tosurround the stress-detecting elements 100 in a substantially annularshape.

Effects of Second Embodiment

The tactile sensor 200 of the second embodiment as described above isprovided with a plurality of stress-detecting elements 100 configured ina two-dimensional array structure in which the stress-detecting elements100 are arranged in the form of a matrix.

Accordingly, the tactile sensor 200 is disposed on, e.g., the sensorsurface with which an object makes contact, and is therefore capable ofdetecting shearing force and positive pressure imparted to the sensorsurface by the object.

In adjacent stress-detecting elements 100, the restriction groove 142 isformed in the elastic body 14. Accordingly, shearing force, positivepressure, and other stress is applied to only the elastic body 14 of apredetermined stress-detecting element 100, and even when the elasticbody 14 bends, it is possible to reduce a drawback in which the bendingof the elastic body 14 is propagated to the elastic body 14 of anadjacent stress-detecting element 100. Therefore, the shearing force andstress that act on an arbitrary position of the tactile sensor 200 canbe accurately detected.

Third Embodiment

The configuration of the gripping device as an example of an electronicapparatus that uses the tactile sensor 200 described above will next bedescribed with reference to the accompanying drawings.

FIG. 8 is a device block view showing the schematic configuration of thegripping device of the third embodiment of the present invention.

In FIG. 8, the gripping device 300 is provided with at least one pair ofgripping arms 310, and is a device for gripping an object Z using thegripping arms 310. For example, the gripping device 300 is a device forgripping and lifting an object conveyed by a belt conveyor or the likein a manufacturing plant or the like for manufacturing a product. Thegripping device 300 is configured to have the gripping arms 310, an armdrive part 320 for driving the gripping arms 310, and a control device330 (signal processing part) for controlling the driving of the armdrive part 320.

The pair of gripping arms 310 are provided with gripping surfaces 311,which are contact surfaces, at the distal end of each arm, and thegripping surfaces 311 make contact with and grip the object Z to therebygrip and lift the object Z. Here, the configuration in which a pair ofthe gripping arms 310 is provided is used as an example in the presentembodiment, but no limitation is imposed thereby, and it is alsopossible to use a configuration in which the object Z is gripped bythree support points using, e.g., three gripping arms 310.

The gripping surfaces 311 provided to the gripping arms 310 have thetactile sensor 200 described in the second embodiment provided to thesurfaces, and the elastic body 14 of surface parts of the tactile sensor200 is exposed. The gripping arms 310 bring the elastic body 14 intocontact with the object Z, and apply a predetermined pressure (positivepressure) to the object Z to thereby grip the object Z. With suchgripping arms 310, the positive pressure applied to the object Z and theshearing force imparted when the object Z attempts to slip and fall fromthe gripping surfaces 311 when the object is gripped are detected by thetactile sensor 200 provided to the gripping surfaces 311, and anelectric signal that corresponds the positive pressure and the shearingforce is outputted to the control device 330.

The arm drive part 320 is a device for moving the pair of gripping arms310 in the direction of mutual approach and separation. The arm drivepart 320 is provided with a holding member 321 for movably holding thegripping arms 310, a drive source 322 for generating a drive force thatmoves the gripping arms 310, and a drive transmission part 323 fortransmitting the drive force of the drive source to the gripping arms310.

The holding member 321 is provided with a guide groove along themovement direction of the gripping arms 310, and the gripping arms 310are held in the guide groove to thereby movably hold the gripping arms310. The holding member 321 is movably provided in the verticaldirection.

The drive source 322 is, e.g., a drive motor that generates drive forcein accordance a drive control signal inputted from the control device330.

The drive transmission part 323 is composed of, e.g., a plurality ofgears, and transmits the drive force generated by the drive source 322to the gripping arms 310 and the holding member 321 to move the grippingarms 310 and the holding member 321.

In the present embodiment, the configuration described above is anexample, but no limitation is imposed thereby. Specifically, nolimitation is imposed by the configuration in which the gripping arms310 are moved along a guide groove of the holding member 321, and it isalso possible to use a configuration in which the gripping arms arerotatably held, or to use another configuration. The drive source 322 isnot limited to being a drive motor, and it is also possible to use aconfiguration in which driving is carried out using, e.g., a hydraulicpump or the like. The drive transmission part 323 is not limited to aconfiguration in which, e.g., the drive force is transmitted using agear, and it is also possible to use a configuration in which the driveforce is transmitted by a belt or a chain, or a configuration providedwith a piston driven by hydraulic pressure or the like.

The control device 330 is connected to the arm drive part 320 and thetactile sensor 200 disposed on the gripping surfaces 311 of the grippingarms 310, and controls the entire operation for gripping the object Z bythe gripping device 300.

Specifically, the control device 330 is connected to the arm drive part320 and the tactile sensor 200, as shown in FIG. 8, and controls theentire operation of the gripping device 300. The control device 330 isprovided with signal-acquiring part 331 for reading detection signalsinputted from the piezoelectric elements 13 in the stress-detectingelements 100 of the tactile sensor 200, stress-calculating part 332 forcalculating shearing force and positive pressure, grip-detecting part333 for detecting the slippage state of the object Z, anddrive-controlling part 334 for outputting a drive control signal to thearm drive part 320 in order to control the driving of the gripping arms310. The control device 330 is provided with a storage part (not shown)for storing positive pressure-related data and shearing force-relateddata that are measured at the time the stress-detecting elements 100 aremanufactured, positive pressure-related data being data that correspondsto the positive pressure and the reference positive pressure signalvalue (V_(top)), and shearing force-related data being data thatcorresponds to the shearing force, the reference X shearing signalvalues (V_(A0), V_(B0)), the reference Y shearing signal values (V_(C0),V_(D0)), the reference X differential absolute value (|V_(A0)−V_(B0)|),and the reference Y differential absolute value (|V_(C0)−V_(D0)|).

The control device 330 may be, e.g., a personal computer or anothergeneral-use computer, and may be configured with, e.g., a keyboard orother input device, a display for displaying the gripped state of theobject Z, or other peripheral devices.

The signal-acquiring part 331, the grip-detecting part 333, and thedrive-controlling part 334 may be stored as a program in, e.g., memoryor another storage part, and suitably read out by a CPU or othercomputing circuit; or may be composed of e.g., an IC or other type ofintegrated circuit that processes inputted electric signals in apredetermined manner.

The signal-acquiring part 331 is connected to the tactile sensor 200 andacquires detection signals inputted from the piezoelectric elements 13in the stress-detecting elements 100 of the tactile sensor 200. Thedetection signals ascertained by the signal-acquiring part 331 areoutputted to and stored in the storage part, and are outputted to thegrip-detecting part 333.

The stress-calculating part 332 calculates the differential value(V_(A)−V_(B)) of the detection signals V_(A), V₁₃ acquired by thesignal-acquiring part 331, and determines whether the values is apositive value or a negative value. Here, in the case that thedifferential value is, e.g., a positive value, it is determined thatshearing force is acting on the elastic body 14 in the +X direction, andin the case that the value is negative, it is determined that shearingforce is acting in the −X direction.

As described above, it is possible to derive|V_(A)−V_(B)|=|V_(A0)−V_(B0)| from the formulas (1) and (2). Therefore,the stress-calculating part 332 can obtain the magnitude of the shearingforce and the reference X shearing signal values V_(A0), V_(B0) based onthe shearing force-related data and the absolute value (|V_(A)−V_(B)|)of the signal differential values thus calculated.

The stress-calculating part 332 furthermore substitutes reference Xshearing signal values V_(A0), V_(B0) into formula (1) or (2) tocalculate the reference positive pressure signal value V_(top), andobtains the positive pressure that corresponds to the reference positivepressure signal value V_(top) from the positive pressure-related data.

The grip-detecting part 333 determines whether the object Z has beengripped by the gripping arms 310 based on the positive pressure and theshearing force calculated by the stress-calculating part 332.

Here, FIG. 9 shows a view of the relationship between the pressing forceand the shearing force that act on the tactile sensor in the grippingoperation of the gripping device 300.

In FIG. 9, the shearing force increases in accordance with the increasein positive pressure until the positive pressure reaches a predeterminedvalue. This state is a state in which a dynamic frictional force isacting between the object Z and the gripping surfaces 311, and thegrip-detecting part 333 determines that gripping is not yet complete ina slipping state in which the object Z is slipping and falling from thegripping surfaces 311. On the other hand, when the positive pressure isequal to or greater than a predetermined value, the state is one inwhich the shearing force does not increase even when the positivepressure is increased. This state is a state in which a staticfrictional force is acting between the object Z and the grippingsurfaces 311, and the grip-detecting part 333 determines that the stateis a gripped state in which the object Z is gripped by the grippingsurfaces 311.

Specifically, it is determined that gripping has been completed in thecase that the value of the shearing force exceeds a predeterminedthreshold value that corresponds to the static frictional force.

The drive-controlling part 334 controls the operation of the arm drivepart 320 based on electric signals detected by the grip-detecting part333.

Effects of Third Embodiment

A tactile sensor 200 of the second embodiment is provided to a grippingdevice 300 such as that described in the third embodiment above. Such atactile sensor 200 is capable of readily detecting shearing force andpositive pressure with favorable precision as described above.Therefore, the gripping operation can be carried out accurately in thegripping device 300 as well based on a high-precision shearing forcedetection signal and positive pressure detection signal.

With such a tactile sensor 200, shearing force can be detected in boththe X direction and the Y direction. Therefore, in the third embodiment,shearing force is measured for lifting object Z, but shearing force canalso be measured in the conveyance direction when, e.g., an objectconveyed on a conveyor belt is to be gripped.

Fourth Embodiment

In the third embodiment described above, a gripping device provided withthe tactile sensor 200 is used as an example of an electronic apparatus,but no limitation is imposed thereby.

In the fourth embodiment, an iron provided with the tactile sensor 200is next described with reference to the accompanying drawings as anotherapplication example of a device that uses the tactile sensor 200.

FIG. 10 is a block view showing the schematic configuration of the ironof the fourth embodiment.

The iron 400 comprises a heater 410, a base part 420, a temperaturesensor 430 disposed in the base part 420, the tactile sensor 200disposed in the base part 420, and a heater drive circuit 440 (signalprocessing part). The heater drive circuit 440 of the iron 400 controlsthe voltage applied to the heater 410 based on a signal from thetemperature sensor 430 and the tactile sensor 200, and heats the basepart 420 to an optimal temperature in relation to a target fabric.

The heater 410 emits heat due to voltage applied from the heater drivecircuit 440 and heats the base part 420.

The base part 420 is a portion that makes contact with target fabric andstretches out wrinkles in the target fabric, and is heated by the heater410. The tactile sensor 200 is disposed in a portion of the base part420, as shown in FIG. 10, and the elastic body 14 of the tactile sensor200 is exposed so as to be capable of contact with the target fabric.

The temperature sensor 430 is disposed in the base part 420, and thetemperature sensor 430 detects and outputs the temperature of the basepart 420 to the heater drive circuit 440.

The heater drive circuit 440 is connected to the tactile sensor 200, thetemperature sensor 430, and the heater 410, and controls the voltageapplied to the heater 410 based on signals from the tactile sensor 200and the temperature sensor 430. The heater drive circuit 440 is providedwith a memory 441, a signal detection part 442, a fabric-distinguishingpart 443, and a temperature controller 444, as shown in FIG. 10.

The heater drive circuit 440 may be configured as, e.g., a computerprovided with a CPU or other computing circuit, and a storage circuit;and the fabric-distinguishing part 443 and temperature controller 444may be configured so as to function as software that is executed bycomputational processing carried out by a computing circuit, or may be,e.g., an IC or other type of integrated circuit that processes inputtedelectric signals in a predetermined manner.

The memory 441 stores positive pressure-related data and shearingforce-related data in the same manner as the storage part of the thirdembodiment described above. The memory 441 also stores stress-roughnessvalue data in which the roughness value of the target fabric is recordedin correlation with the stress detected by the tactile sensor 200. Anexample of the stress-roughness value is a roughness value recorded foreach positive pressure in correlation with the shearing force.

The roughness-temperature data in which the optimal temperature of thebase part 420 is recorded in correlation with the roughness value may bestored in the memory 441.

The signal detection part 442 is connected to the tactile sensor 200 andacquires the signal detection signals (V_(A), V_(B), V_(C), V_(D))inputted from the tactile sensor 200. The signal detection part 442calculates the positive pressure and the shearing force based on thedetection signals thus acquired, the positive pressure-related data, theshearing force-related data, and the formulas (1) to (4), using the samemethod as that of the stress-calculating part 332 in the thirdembodiment.

The fabric-distinguishing part 443 discriminates the type of targetfabric based on the shearing force and positive pressure calculated bythe signal detection part 442, and the stress-roughness value datastored in the memory 441.

For example, in the present embodiment, the roughness that correspondsto the shearing force is stored as stress-roughness data for eachpositive pressure. In this case, the fabric-distinguishing part 443reads from the memory 441 the stress-roughness value data thatcorresponds to the positive pressure, and acquires from thestress-roughness value data the roughness value that corresponds to theshearing force.

The fabric-distinguishing part 443 outputs the roughness value thusacquired to the temperature controller 444.

The temperature controller 444 controls the voltage applied to theheater 410 based on the roughness value inputted from thefabric-distinguishing part 443 and the temperature of the base part 420detected by the temperature sensor 430.

Specifically, the temperature controller 444 reads theroughness-temperature data from the memory 441 and acquires the optimaltemperature of the base part 420 that corresponds to the roughness valueinputted from the fabric-distinguishing part 443. The temperaturecontroller 444 calculates the required voltage value to be applied tothe heater 410 from the differential value between the optimaltemperature and the detected temperature inputted from the temperaturesensor 430, in order to set the base part 420 to an optimal temperature,and then applies the voltage to the heater 410.

Effects of Fourth Embodiment

The tactile sensor 200 of the third embodiment is provided to the iron400 of the fourth embodiment as described above. Such a tactile sensor200 can readily detect shearing force and positive pressure withfavorable precision, as described above. Therefore, positive pressureand shearing force can be detected with high precision in the iron 400when the target fabric comes into contact with the base part 420.

Using the fabric-distinguishing part 443, the heater drive circuit 440of the iron 400 is capable of discriminating the roughness of the targetfabric that corresponds to the detected positive pressure and shearingforce. Therefore, the type of target fabric can be determined from theroughness of the target fabric thus determined, and the temperaturecontroller 444 can set the temperature of the base part 420 incorrespondence with the type of fabric. Therefore, in the iron 400, thetemperature of the base part 420 can be automatically set incorrespondence with the fabric, and the laborious work of changing thetemperature setting that corresponds to the type of the target fabriccan be forgone.

In the fourth embodiment, an example is described in which the roughnessvalue that corresponds to the positive pressure and shearing force isrecorded in the stress-roughness value data, which is stored in thememory 441, but it is also possible to use a configuration such as onein which, e.g., the type of target fabric that corresponds to thepositive pressure and shearing force is recorded in stress-fabric typedata, which is stored in the memory 441. In this case, thefabric-distinguishing part 443 directly discriminates the type of targetfabric that corresponds to the positive pressure and shearing force, andthe temperature controller 444 acquires the temperature that correspondsto the type of fabric thus discriminated.

The optimal temperature of the base part 420 that corresponds to thepositive pressure and shearing force may be recorded instress-temperature data, which may be stored as correlation data. Inthis case, the roughness-temperature data is not required to be stored,and it is possible to provide an iron 400 in which the temperature ofthe base part 420 can be automatically set using a lesser amount ofdata.

In the iron 400, an example was described in which the temperature ofthe base part 420 is automatically set by the heater drive circuit 440,but it is also possible to use a configuration in which it is possibleto switch as appropriate between an automatic mode for automaticallysetting the temperature of the base part 420 and a manual mode formanually setting the temperature.

Fifth Embodiment

A fifth embodiment is next described with reference to the accompanyingdrawings.

In the fifth embodiment, a notebook computer 500 provided with thetactile sensor 200 is used as another example of the electronicapparatus of the present invention.

FIG. 11 is a perspective view showing the schematic configuration of thenotebook computer 500 of the fifth embodiment.

In FIG. 11, the notebook computer 500 is provided with a device mainbody 510, a display 520, a first input part 530, and a second input part540.

The display 520 is composed of, e.g., a liquid-crystal panel, an organicpanel, or the like; is connected to the computing controller (not shown)accommodated inside the device main body 510; and is configured so as todisplay various operational images and other information using thecomputing controller.

The first input part 530 is composed of a keyboard, a numerical keypad,or the like.

The second input part 540 is disposed in a position in front of thefirst input part 530, and the tactile sensor 200 described above is usedas the second input part 540. The surface of the elastic body 14 of thetactile sensor 200 is exposed on the surface of the second input part540, as shown in FIG. 11, and the user moves a finger or moves a stylusor the like on the surface of the elastic body 14, whereupon a shearingforce and/or positive pressure is generated by these movements. Theshearing force and positive pressure are detected, whereby the contactposition coordinates and movement direction of the user finger and/ortouch pen can be detected and outputted as an electric signal. Thedetails of the input operation desired by the user can be accuratelyascertained based on the outputted electric signal, and the operabilityof the notebook computer 500 can be improved.

Other Embodiments

The present invention is not limited to the embodiments described above,and modifications, improvements, and the like that are within a range inwhich the objects of the present invention can be achieved are alsoincluded in the present invention.

For example, described in the first embodiment is a stress-detectingelement 100 capable of detecting both shearing force in the X directionand shearing force in the Y direction, but it is also possible to use astress-detecting element for detecting, e.g., shearing force andpositive pressure in the X direction, as shown in FIG. 12. In FIG. 1,portions of the piezoelectric elements 13A and 13B are shown in solidlines to better understand the structures thereof although thepiezoelectric elements 13A and 13B are disposed below the elastic body14.

In FIG. 12, the stress-detecting element 100A is a detection element fordetecting the shearing force and pressing force in the X direction, andcomprises the sensor substrate 11 provided with the opening part 111having a pair of mutually parallel rectilinear sections (firstrectilinear section 111A, second rectilinear section 111B), the supportfilm 12, the piezoelectric elements 13 (first piezoelectric element 13Aand second piezoelectric element 13B), and the elastic body 14. FIG. 12shows an example in which the opening part 111 is formed in the shape ofa rectangle, but any shape may be used provided that sinusoidal bendingis generated in the membrane 121 when the shearing force is applied inthe X direction. Therefore, it is possible to form an opening part 111provided with the first rectilinear section 111A, the second rectilinearsection 111B, and semicircular curved parts that connect the two endparts of the first rectilinear section 111A and the second rectilinearsection 111B together.

In the stress-detecting element 100, 100A, a configuration is used fordetecting shearing force and positive pressure in the X direction usingboth the first piezoelectric element 13A and the second piezoelectricelement 13B, but it is also possible to dispose the first piezoelectricelement 13A only along the first rectilinear section 111A, and leave theother second rectilinear section 111B without a piezoelectric element.

Furthermore, a configuration is used in the stress-detecting elements100, 100A in which a hollow part 144 formed by the slit 141 is incommunication with the exterior and a portion of the membrane 121 isexposed to the exterior, and when an object makes contact with theelastic parts 141A, 141B, 141C, 141D, shearing force is transmitted fromthe object to the membrane 121. However, no limitation is imposedthereby. For example, it is possible to use a configuration in which acontact film that makes contact with an object is disposed on the upperpart of the elastic parts 141A, 141B, 141C, 141D, and a slit 141 isblocked off by the contact film. Such a contact film can be formed usingthe same material as the elastic parts 141A, 141B, 141C, 141D. Contactbetween the membrane 121 and an object can be prevented by providingsuch a contact film, and the membrane 121 can be protected.

In the second embodiment, a configuration is described in which arestriction groove 142 is formed in the elastic body 14 between mutuallyadjacent stress-detecting elements 100, as shown in FIGS. 9 and 10, butno limitation is imposed thereby. For example, it is also possible touse a configuration in which the restriction groove 142 is not formed,and in this case, the distance between the stress-detecting element 100is ensured, thereby making it possible to reduce the propagation ofbending from the elastic body 14 of the mutually adjacentstress-detecting elements 100. It is also possible to use aconfiguration in which an area separation member having greater rigiditythan the elastic body 14 is disposed between mutually adjacentstress-detecting elements 100. In such a configuration, the amount ofbending of the elastic body 14 is reduced because the area separationmember, which has greater rigidity than the configuration in which therestriction groove 142 is disposed, is formed at the periphery of theelastic body 14, and it is possible to reduce the propagation of bendingof the elastic body 14 from mutually adjacent stress-detecting elements100.

In the first embodiment, a configuration is used in which the upperelectrode 133 and lower electrode 131 are disposed in positions that donot mutually overlap when the sensor is viewed in a plan view such thatthe two electrodes do not make contact with each other, but notlimitation is imposed thereby. For example, it is also possible to use aconfiguration in which the upper electrode 133 and the lower electrode131 are disposed in positions that have overlapping portions when thesensor is viewed in a plan view provided that an insulating film isformed between the upper electrode 133 and the lower electrode 131.

An example is described in which the support body of the presentinvention is composed of a single sensor substrate 11, but it is alsopossible to use a configuration in which a single support substrate(support body) is disposed for each stress-detecting element 100, andthe tactile sensor 200 is formed by securing these support substratesonto the sensor substrate.

The best modes for carrying out the present invention are described indetail above, but the present invention is not limited thereto.Specifically, the present invention has mainly been depicted anddescribed in particular with relation to specific embodiments, butvarious modification and improvements can be made to the embodimentsdescribed above by a person skilled in the art without departing fromthe technical concepts and the scope of the objects of the presentinvention.

GENERAL INTERPRETATION OF TERMS

In understanding the scope of the present invention, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. Also, the terms “part,” “section,” “portion,” “member” or“element” when used in the singular can have the dual meaning of asingle part or a plurality of parts. Finally, terms of degree such as“substantially”, “about” and “approximately” as used herein mean areasonable amount of deviation of the modified term such that the endresult is not significantly changed. For example, these terms can beconstrued as including a deviation of at least ±5% of the modified termif this deviation would not negate the meaning of the word it modifies.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. Furthermore, the foregoing descriptions of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A stress-detecting element comprising: a supportbody having an opening part with a first rectilinear section and asecond rectilinear section extending parallel to each other; a supportfilm disposed over the support body and blocking off the opening part; afirst piezoelectric element disposed over the support film along thefirst rectilinear section of the opening part of the support body so asto straddle the first rectilinear section from an interior area of theopening part to an exterior area of the opening part as seen in planview along a film thickness direction of the support film, the firstpiezoelectric element being configured and arranged to output anelectric signal upon deformation; a first elastic part disposed over thesupport film along the first rectilinear section of the opening part ofthe support body so as to straddle the first rectilinear section fromthe interior area of the opening part to the exterior area of theopening part as seen in plan view, the first elastic part having a firstelastic end section disposed in the interior area of the opening part asseen in plan view; and a second elastic part disposed over the supportfilm along the second rectilinear section of the opening part of thesupport body so as to straddle the second rectilinear section from theinterior area of the opening part to the exterior area of the openingpart as seen in plan view, the second elastic part having a secondelastic end section disposed in the interior area of the opening part asseen in plan view, the second elastic end section being spaced apartfrom the first elastic end section, wherein the first elastic endsection of the first elastic part and the second elastic end section ofthe second elastic part are parallel to the first rectilinear sectionand the second rectilinear section as seen in plan view, a distance fromthe first rectilinear section of the opening part to the first elasticend section is equal to a distance from the second rectilinear sectionto the second elastic end section as seen in plan view, and each of thedistance from the first rectilinear section of the opening part to thefirst elastic end section and the distance from the second rectilinearsection to the second elastic end section is 10% to 30% of a distancefrom the first rectilinear section to the second rectilinear section. 2.The stress-detecting element recited in claim 1, wherein the firstelastic part covers the first piezoelectric element.
 3. Thestress-detecting element recited in claim 1, further comprising a secondpiezoelectric element disposed over the support film along the secondrectilinear section of the opening part of the support body so as tostraddle the second rectilinear section from the interior area of theopening part to the exterior area of the opening part as seen in planview, the second piezoelectric element being configured and arranged tooutput an electric signal upon deformation.
 4. The stress-detectingelement recited in claim 1, wherein the opening part further includes athird rectilinear section and a fourth rectilinear section extendingorthogonal to the first rectilinear section and the second rectilinearsection, the stress-detecting element further comprising a thirdpiezoelectric element disposed over the support film along the thirdrectilinear section of the opening part of the support body so as tostraddle the third rectilinear section from the interior area of theopening part to the exterior area of the opening part as seen in planview, the third piezoelectric element being configured and arranged tooutput an electric signal upon deformation; a third elastic partdisposed over the support film along the third rectilinear section ofthe opening part of the support body so as to straddle the thirdrectilinear section from the interior area of the opening part to theexterior area of the opening part when viewed in the plan view, thethird elastic part having a third elastic end section disposed in theinterior area of the opening part as seen in plan view; and a fourthelastic part disposed over the support film along the fourth rectilinearsection of the opening part of the support body so as to straddle thefourth rectilinear section from the interior area of the opening part tothe exterior area of the opening part as seen in plan view, the fourthelastic part having a fourth elastic end section disposed in theinterior area of the opening part as seen in plan view, the fourthelastic end section being spaced apart from the third elastic endsection.
 5. The stress-detecting element recited in claim 4, furthercomprising a fourth piezoelectric element disposed over the support filmalong the fourth rectilinear section of the opening part of the supportbody so as to straddle the fourth rectilinear section from the interiorarea of the opening part to the exterior area of the opening part asseen in plan view, the fourth piezoelectric element being configured andarranged to output an electrical signal upon deformation.
 6. Thestress-detecting element recited in claim 4, wherein the first elasticpart, the second elastic part, the third elastic part, and the fourthelastic part are integrally formed as one-piece, unitary member.
 7. Asensor module comprising: a sensor array including a plurality of thestress-detecting elements recited in claim 1 that are arranged in a formof an array.
 8. An electronic apparatus comprising: the sensor modulerecited in claim 7; and a signal processing part configured and arrangedto process electrical signals outputted from the sensor module.